Efficient superantioxidant and biofuel production from microalga Haematococcus pluvialis via a biorefinery approach

A biorefinery approach was implemented to produce a superantixoident, i.e., astaxanthin, and biofuels, i.e., ethanol and biogas, from the biomass of microalga Haematococcus pluvialis. The hydrolysis of residual biomass obtained from astaxanthin extraction was conducted using α-amylase and glucoamylase for hydrolysis of α-glucans and a mixture of cellulases for β-glucan hydrolysis. Four different hyudrolysis processes were employed and the efficiency of 97.2% over the total residual glucan was obtained, which was then fermented to produce 0.21 g ethanol/g residual biomass. The residuals obtained from astaxanthin extraction and fermentation were anaerobically digested to produce biomethane. The yield of biomethane was 264.8 ml/g volatile solids, 2.9 fold greater than methane yield from raw microalgal biomass. Overall, the process of astaxanthin extraction and consecutive production of ethanol and biogas from H. pluvialis biomass was recognized as a promising process to produce 45.8 g astaxanthin and 7095.3 KJ energy per Kg of raw biomass.